Terahertz Scanless Hypertemporal Imaging

Abstract

Since its first demonstration in 1995, terahertz time‐domain imaging has attracted an increasingly growing interest for its ability to reveal spectral fingerprints of materials and probe changes in refractive index and absorption, as well as detect the inner structure of complex objects via time‐of‐flight measurements. Practically, however, its widespread use has been hampered by the very long acquisition time typically required to spatially raster‐scan the object, and for each spatial point, record the field in time via a delay line. Here, this fundamental bottleneck is addressed by implementing a scanless single‐pixel imaging scheme, which sets the path for an unprecedented reduction of both system complexity and acquisition time. By properly exploiting natural wave diffraction, time‐to‐space encoding applied to terahertz point detection allows for an almost instantaneous capture of the terahertz waveforms, while multidimensional images are reconstructed via a computational approach. The scheme is a promising solution for the development of next‐generation fast and compact terahertz imagers perfectly suitable for high‐repetition‐rate laser sources.

Single-shot pump-probe technique by the combination of an echelon and a grating with a time window of 109 ps

“…In addition to the above encoding strategies, the use of a grating or a digital micromirror device has shown promise [17][18][19][20]. However, few studies on this topic exist, and the time window, to the best of our knowledge, has not exceeded 30 ps.…”

Dual-grating single-shot pump-probe technique

“…In this strategy, the time delay is mapped to different spatial positions of the probe beam, and then the intensity distribution of the probe beam is recorded by using the CCD/CMOS camera, thereby realizing single-shot dynamic measurements. At present, the main spatial encoding strategies include the echelon encoding strategy [2][3][4][5][6][7], angle beam encoding strategy [8][9][10][11][12], and grating encoding strategy [13][14][15][16]. As far as we know, the reported maximum time window of the echelon coding strategy is ~ 37.7 ps, and the phase difference of the echelon surface can lead to the image blurring problem, which is the main reason that limits the larger time window for the echelon encoding strategy [6].…”

Dual-grating single-shot pump-probe technique

“…In this strategy, the time delay is mapped to different spatial positions of the probe beam, and then the intensity distribution of the probe beam is recorded using a CCD/CMOS camera, thereby realizing single-shot dynamic measurements. At present, the main spatial encoding strategies include the echelon encoding strategy [6,7,[9][10][11][12], angle beam encoding strategy [13][14][15][16][17], and grating encoding strategy [18][19][20][21]. As far as we know, the reported maximum time window of the echelon coding strategy is ~ 37.7 ps, and the phase difference of the echelon surface can lead to the image blurring problem, which is the main reason that limits the larger time window for the echelon encoding strategy [11].…”